Yes you do in Texas. Below is From the Texas state code one of the requirements for self defense.
this is the reason in most situations that a man robbing someone at gunpoint gets charged with murder and not self defense when they shoot someone trying to stop them with a weapon. Ie. you get shot and killed trying to shoot and stop an armed robber. That armed robber doesn’t get to claim self defense.
“3) was not otherwise engaged in criminal activity, other than a Class C misdemeanor that is a violation of a law or ordinance regulating traffic at the time the force was used.”
No, you don't in Texas. What you quoted was a condition for presumption. Here is the earlier part of the subsection of the statute that the condition applies to:
"Sec. 9.31. SELF-DEFENSE. (a) Except as provided in Subsection (b), a person is justified in using force against another when and to the degree the actor reasonably believes the force is immediately necessary to protect the actor against the other's use or attempted use of unlawful force. The actor's belief that the force was immediately necessary as described by this subsection is presumed to be reasonable if the actor:"
The condition you quoted in 3) is relevant to whether or not the use of force in self-defense was or was not presumed to be reasonable. So if someone is engaged in criminal activity, they do not automatically have the benefit of being presumed to be reasonable. This means that in court, there is not a presumption that the use of self-defense was or was not reasonable (it may have been reasonable, or it may not have been reasonable; it's just not presumed either way).
You mention a case related to a robbery. I agree that the situation you described doesn't qualify as self-defense, but not because of subsection 3) that you quoted. It's because, as stated later in the same statute, the robber provoked the victim's use of force. A robber provoking someone with a lethal weapon while robbing them does not allow for self-defense if the robber ends up protecting themselves from harm from the victim in this case; in fact, it gives the victim a right to self-defense.
But in other instances (including in Texas), engaging in criminal activity doesn't remove self-defense rights. As an example, if someone is walking down the street minding their own business and a stranger suddenly attacks them with a knife, they have the right to use deadly force for self-defense, even if they had on a backpack full (felony quantity, let's say) of illegal drugs at the time. Due to your C) quote above, the force used by the backpacker/drug dealer will not be presumed to be reasonable, yet the use of force for self-defense would end up being demonstrated as legally justified.
Either way, though, I don't see that the shooter in the video we're discussing has a case for self-defense.